I just bought a MacBook and didn't use OS X for some time now. I'm not sure if I should use an antivirus and which one. The best weapon to stay away from virus is common sense in my opinion. But still sometimes I'm pretty paranoid: like some days ago I went to some movie streaming site and I got so many pop-ups, and also a download started automatically (a dmg that I obviously didn't open). One of the pop-up was Mac Keeper that appears to be a site that want you to download his antivirus or some **** like this. What do you suggest? Any tips you can share on how I should stay safe or how attacks happens on OS X?